Inner-valence photoionization of HCN: An example of the complete breakdownof the quasiparticle picture of photoionization

We performed both single- and coupled-channel scattering calculations of th e photoionization of HCN at a photon energy range of 40-1000 eV. Based upon the present results, we predict that HCN is a system for which the inner-v alence photoionization is characterized by a complete breakdown of the quas iparticle picture of photoionization. We find that there is no inner valenc e main line and that the intensity from photoionization from the inner vale nce 3 sigma orbital is split into two prominent satellites and two weaker s atellites. These four satellites occur at binding energies of approximately 27.0, 29.5, 31.0, and 33.0 eV, and are almost solely of inner valence orig in. We identify these satellites as being of inner-valence origin as a cons equence of the theoretically predicted high-energy convergence of the photo ionization cross-section rations to the ratio of corresponding spectroscopi c intensity factors. Additionally, we find that there is one mixed provenan ce satellite that occurs on the shoulder of the highest binding energy.(4 s igma(-1)) line at 22.5 eV, i.e., lower than the expected energy range for s atellites. The existence of this satellite is another result of the breakdo wn of the quasiparticle picture. On a phenomenological basis, all four of t he inner-valence-derived satellites appear to be dynamically correlated sha ke-up states. [S1050-2947(99)02711-0].